E-beam lithography using chemically amplified resists plays an important role in the fabrication of masks. The successful preparation of chemically amplified resists requires the optimization of at least the following parameters: resist formulation, speed of fabrication, film sensitivity, etch resolution, and line-edge roughness (LER).
Chemically amplified resists are typically spun on the top of a 15 nm Cr layer. In order to successfully transfer the pattern onto the metal layer, the chemically amplified resists must have good etch properties. The etch rate and isotropy or anisotropy of the film determine the required film thickness with higher etch rates requiring thicker resist films and lower etch rates being amenable to thinner resist films.
Resists that operate over a wide range of post exposure bake temperatures are preferred in the art; however, the critical dimensions (CD) should vary minimally with small temperature fluctuations.